Well, I wish I could say that I have been successful at ppc but I haven't yet been able to try.
However, I did watch a wso that was very enlightening. It basically showed how to find the traffic.
See most ppl find a product first, then try to figure out how to market it. I think it's better to find traffic first, then find product for ppl. Either way PPC really boils down to demographics.
For instance, lets say you have financial based product. Maybe it would be best to buy ad spots at cnn.com, forbes.com, foxnews.com, msnfinancial.com, where as if you are selling beauty products you might do better at betterhomesandgardens, or elle.com etc.
So how do you know what demographic is going to what webiste? Alexa rankings. just go to alex.com and you can find out what type of demographic visits any major site on the net.
Once you find the right sources then it comes down to split testing.
Ok, hope this helped. Peace.